U.S. patent application number 12/506636 was filed with the patent office on 2010-08-05 for hybrid supercapacitor using transition metal oxide aerogel.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Jun-Hee BAE, Hyun-Chul JUNG, Hak-Kwan KIM, Soung-Hyun RA.
Application Number | 20100195268 12/506636 |
Document ID | / |
Family ID | 42397533 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100195268 |
Kind Code |
A1 |
KIM; Hak-Kwan ; et
al. |
August 5, 2010 |
HYBRID SUPERCAPACITOR USING TRANSITION METAL OXIDE AEROGEL
Abstract
It discloses a hybrid supercapacitor including a carbon aerogel
cathode and a transition metal oxide aerogel anode which is able to
increase energy density and power density with increase of overall
cell potential and at the same time lower internal resistance of
the electrode and equivalent series resistance by using a
monolithic electrode with no use of current collector and
binder.
Inventors: |
KIM; Hak-Kwan; (Hanam-si,
KR) ; RA; Soung-Hyun; (Seongnam-si, KR) ; BAE;
Jun-Hee; (Suwon-si, KR) ; JUNG; Hyun-Chul;
(Yongin-si, KR) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
42397533 |
Appl. No.: |
12/506636 |
Filed: |
July 21, 2009 |
Current U.S.
Class: |
361/502 ;
29/25.03 |
Current CPC
Class: |
H01G 9/155 20130101;
H01G 11/22 20130101; H01G 11/46 20130101; Y02E 60/13 20130101 |
Class at
Publication: |
361/502 ;
29/25.03 |
International
Class: |
H01G 9/00 20060101
H01G009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2009 |
KR |
10-2009-0008587 |
Claims
1. A hybrid supercapacitor comprising: a carbon aerogel cathode;
and a transition metal oxide aerogel anode.
2. The hybrid supercapacitor of claim 1, wherein the carbon aerogel
cathode has a pore size distribution of a mesopore size of 20 nm or
higher.
3. The hybrid supercapacitor of claim 1, wherein the carbon aerogel
of the carbon aerogel cathode is prepared by a method comprising:
preparing a resorcinol-formaldehyde sol solution; immersing the sol
solution into carbon paper and drying; and pyrolizing the
immersed-dried paper.
4. The hybrid supercapacitor of claim 1, wherein the transition
metal oxide of the transition metal oxide aerogel anode is selected
from the group consisting of MnO.sub.2, RuO.sub.2, CoO and NiO.
5. The hybrid supercapacitor of claim 1, wherein the transition
metal oxide aerogel is prepared by employing a sol-gel process from
a precursor of the transition metal oxide.
6. A method for manufacturing a hybrid supercapacitor comprising:
preparing a carbon aerogel cathode; preparing a transition metal
oxide aerogel anode; and preparing a hybrid capacitor by employing
the cathode and the anode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2009-0008587 filed on Feb. 3, 2009, with the
Korea Intellectual Property Office, the contents of which are
incorporated here by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] It relates to a hybrid supercapacitor including a carbon
aerogel cathode and a transition metal oxide aerogel anode.
[0004] 2. Description of the Related Art
[0005] Higher value-added businesses which collect and use various
and useful information in real time by employing IT equipments
receives attentions and stable energy supply for securing
reliability of such systems becomes an important factor in the
information-oriented society. These IT equipments and electrical
devices include electric circuit boards and each circuit board has
a capacitor which stores an electric charge and releases it when
required and thus stabilizes energy flow in the circuit. This
capacitor has a very short charge/discharge time, a long lifetime
and a high power density but generally a very low energy density.
This disadvantage of low energy density causes many limitations on
its use as an energy storage device.
[0006] However, electrochemical capacitors, supercapacitors or
ultracapacitors, which have started to be commercialized in Japan,
Russia, USA, etc. since 1995, are under development in all
countries of the world to provide higher energy density as next
generation energy storage devices along with secondary
batteries.
[0007] A supercapacitor can be broadly classified into 3 categories
depending on the electrode and the mechanism: (1) an electric
double layer capacitor (EDLC) which employs activated carbon as an
electrode and is based on an electric double layer electric charge
absorption mechanism; (2) a metal oxide electrode pseudocapacitor
(or redox capacitor) which employs a transition metal oxide and a
conductive polymer as an electrode material and is based on a
pseudo-capacitance mechanism; and (3) a hybrid capacitor which
combines the features of both electrochemical and electrolytic
capacitors. Among them, the EDL-type supercapacitor using activated
carbons is currently used the most.
[0008] The supercapacitor is composed of electrode, electrolyte,
current collector, and separator and is based on the
electrochemical mechanism which stores energy through absorption of
electrolyte ions on the electrode surface by migrating along with
the electric field when voltages are applied on the both ends of a
unit cell electrode. Since the specific capacitance is proportional
to the specific surface area, the supercapacitor improves energy
(storage) density through the use of an activated carbon electrode,
which is a porous material. An electrode is manufactured by
preparing slurry including a carbon electrode material, a carbon
conductive material and a polymer binder and coating the slurry on
a current collector. Here, it is important to improve adhesiveness
to the current collector and reduce contact resistance at the same
time and further lower internal contact resistance between
activated carbons by changing a ratio or kind of the binder, the
conductive material and the electrode material.
[0009] When a pseudocapacitor using a metal oxide electrode
material is used, the transition metal oxide exhibits higher
capacity and higher power density compared to activated carbons.
Recently, it has been reported that amorphous hydrate electrodes
exhibit much higher specific capacitance.
[0010] However, even though it provides higher electric
capacitance, its manufacturing cost is more than twice higher,
manufacturing is more difficult and equivalent series resistance is
increased, compared with the EDLC.
[0011] Thus, studies on hybrid capacitors, which employ an
asymmetric electrode by combining the best features of the EDLC and
the pseudocapacitor, are increasing to improve actuation voltages
and energy density. However, even though the hybrid capacitor
improves electric capacitance and energy density, it is not
generalized yet and due to its nonlinarity, its properties such as
charge/discharge properties are not ideal.
SUMMARY
[0012] It provides a hybrid supercapacitor which is able to
increase energy density and power density with increase of overall
cell potential and lower internal resistance of the electrode and
equivalent series resistance by using a monolithic electrode
without using a current collector and a binder.
[0013] According to an aspect of embodiments, there is provided a
hybrid supercapacitor including a carbon aerogel cathode; and a
transition metal oxide aerogel anode.
[0014] The carbon aerogel cathode may have a pore size distribution
of a mesopore size of 20 nm or higher. The carbon aerogel of the
carbon aerogel cathode may be prepared by a method including:
preparing a resorcinol-formaldehyde sol solution; immersing the sol
solution into carbon paper and drying; and pyrolizing the dried
paper.
[0015] The transition metal oxide of the transition metal oxide
aerogel anode may be chosen from MnO.sub.2, RuO.sub.2, CoO and NiO.
The transition metal oxide aerogel anode may be prepared by the
sol-gel process through the reduction of transition metal oxide
precursor.
[0016] According to another aspect of embodiments, there is
provided a method for manufacturing a hybrid supercapacitor
including: preparing a carbon aerogel cathode; preparing a
transition metal oxide aerogel anode; and preparing a hybrid
capacitor by employing the cathode and the anode.
[0017] The hybrid supercapacitor may control parameters not to form
micropores having a size of not contributing substantial
capacitance during the manufacturing process of the aerogel cathode
and anode and further improve capacitance by optimizing an
effective contact area between an electrolyte solution and an
electrode since it is a monolith type which is not necessary to use
any binder.
[0018] The hybrid supercapacitor may resolve a contact resistance
problem which can be caused in the boundary between an electrode
and a current collector since it is a monolith type which is not
necessary to use any current collector.
[0019] Therefore, the hybrid supercapacitor may increase energy and
power density with increase of over all cell potential which is
advantages of the hybrid-type supercapacitor and at the same time
minimize the electrode internal resistance and the equivalent
series resistance (ESR) since it is a monolith type which is not
necessary to use any current collector and binder
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic view of a monolithic hybrid
supercapacitor according to an embodiment.
[0021] FIG. 2 is a SEM picture (low magnification) of activated
carbon powders.
[0022] FIG. 3 is a SEM picture (high magnification) of activated
carbon powders.
[0023] FIG. 4 is a SEM picture (low magnification) of the surface
of a monolithic carbon aerogel according to an embodiment.
[0024] FIG. 5 is a SEM picture (high magnification) of the surface
of a monolithic carbon aerogel according to an embodiment.
[0025] FIG. 6 is a CV (cyclic voltammetry) graph illustrating the
charge-discharge result of a hybrid supercapacitor prepared in
Example.
[0026] FIG. 7 is a CV (cyclic voltammetry) graph illustrating the
charge-discharge result of a hybrid supercapacitor prepared in
Comparison Example.
[0027] Hereinafter, preferred embodiments will be described in
detail of the hybrid supercapacitor.
[0028] The hybrid supercapacitor may include a carbon aerogel
cathode; and a transition metal oxide aerogel anode and further
include a separator and an electrolyte.
[0029] Carbon Aerogel Cathode
[0030] A material having a high specific area may be used as an
electrode material to improve the electric capacitance of a
supercapacitor since the capacitance is proportional to the area of
an electrode. Further, the supercapacitor may have superior
electronic conductivity, electrochemical inactivity, formability,
processability and the like and porous carbon materials having such
properties have been generally used. Examples of the porous carbon
material may include activated carbons, activated carbon fibers,
amorphous carbons, carbon aerogels, carbon composites, carbon
nanotubes and the like.
[0031] However, even though the activated carbons have high
specific area, effective pores of the activated carbon is only
about 20% because most pores are micropores of which diameter is
about 20 nm or less and which cannot server as an electrode. Since
the electrode is prepared from slurry which is formed by mixing
binder, carbon conducting material and solvent, etc. an actual
effective contact area between an electrode and an electrolyte is
decreased. There are further drawbacks such as uneven electric
capacitance and contact resistance between an electrode and a
current collector.
[0032] The hybrid supercapacitor may employ a monolith carbon
aerogel cathode.
[0033] The term "monolith type or monolithic" may be an integrally
formed electrode which thus does not require use of a binder and a
current collector.
[0034] The term "aerogel" may be a solid-state material derived
from gel in which the liquid component of the gel is replaced with
gas and have a net-work structure with a high porosity. The aerogel
may be used as a monolithic electrode since it is formed integrally
and thus does not require the use of binder and current
collector.
[0035] According to an embodiment, the carbon aerogel of the
monolith carbon aerogel cathode may be prepared by preparing a
porous polymer using an organic material through a sol-gel process
and pyrolizing the porous polymer.
[0036] The sol-gel process may include preparing a solution by
dissolving an organic monomer, an aldehyde and a surfactant, etc in
a solvent such as water, stirring the solution, polymerizing the
solution at an appropriate temperature, and removing the solvent by
drying and isolating, etc.
[0037] In the sol-gel process, the organic material may be an
organic monomer including hydroxyl or amine groups of which example
may include resorcinol, phenol, melamine, biphenol and sucrose,
etc. and examples of the aldehyde may include formaldehyde and
acetaldehyde, etc.
[0038] The pyrolysis may be performed at a temperature of
700-1050.degree. C. under an inert atmosphere such as nitrogen
gas.
[0039] For example, in order to prepare carbon aerogel by the
sol-gel process and the pyrolysis, resorcinol (R), formaldehyde (F)
and sodium carbonate, which is a basic catalyst, are condensed at
an aqueous phase, in various catalyst ratios (R/C). The sol
solution from the condensation at an aqueous phase may be immersed
into carbon paper and the result may be fixed between glass plates
and dried in a closed container to prevent evaporation of the RF
carbon paper. The carbon paper-immersed RF aerogel composite may be
obtained after the remained water is substituted with acetone or
the like and then pyrolized at a high temperature (700-1050.degree.
C.) under N.sub.2 to provide monolith carbon aerogel. The monolith
carbon aerogel is CO.sub.2 activated by injecting CO.sub.2 into the
monolith carbon aerogel at a high temperature to increase effective
pores.
[0040] A size of carbon aerogel may be controlled by adjusting
parameters during the manufacturing process.
[0041] When a mole ratio of the organic monomer is increased while
fixing concentration parameters of other components, size of
agglomerated clusters is increased. Since spaces between clusters
become pores, when the size of clusters increases with increase of
the organic monomer mole ratio, the size of pores between clusters
also increases. On the other hand, when a mole ratio of a
surfactant is increased while fixing concentration parameters of
other components, size of agglomerated clusters is decreased and
thus size of pores becomes decreased. Thus, the pore size and ratio
may be controlled by adjusting such parameters.
[0042] The monolith carbon aerogel prepared by the above method may
be used as a cathode material by cutting it in an electrode size
and since the carbon aerogel has excellent conductivity, it may be
produced into an electrode by connecting lead wires without using a
current collector.
[0043] Even though the specific area of the carbon aerogel prepared
by the above method is similar to that of conventional activated
carbon (700-1000 m.sup.2/g), it has much more effective pores of
which diameter is 20 nm or higher and much less contact area with
an electrolyte since any binder is not used. Further, there is
little risk of reduction of energy density due to the contact
resistance because an electrode is prepared without using a current
collector.
[0044] Transition Metal Oxide Aerogel Anode
[0045] A hybrid supercapacitor may use a monolith transition metal
oxide aerogel anode.
[0046] According to an embodiment, a transition metal oxide which
can be used for the monolith transition metal oxide aerogel anode
may be chosen from MnO.sub.2, RuO.sub.2, CoO and NiO.
[0047] According to an embodiment, the transition metal oxide
aerogel anode may be prepared by employing the sol-gel process
through the reduction of a transition metal oxide precursor. The
transition metal oxide precursor may be KMnO.sub.4, NaMnO.sub.4,
K.sub.2RuO.sub.4, Na.sub.2RuO.sub.4, KCoO.sub.2, NaCoO.sub.2,
KNiO.sub.2, NaNiO.sub.2, or the like.
[0048] A method for preparing MnO.sub.2 aerogels may be used in
Bach et al., J. Solid State Chem. 88 (1990) 325 and Long et al., J.
Non-Crystalline solids 285 (2001) 288.
[0049] A pore size of the transition metal oxide aerogel may be
controlled by adjusting parameters during the manufacturing
process.
[0050] The monolith transition metal oxide aerogel prepared by the
above method may be used as an anode material by cutting into an
electrode size and since the transition metal oxide aerogel has
excellent conductivity, it may be produced into an electrode by
connecting lead wires without using a current collector.
[0051] The electrode has far superior electric conductivity
compared with transition metal oxides and still keeps
characteristics of pseudo-capacitances
[0052] Separator
[0053] A separator prevents internal short circuits between cathode
and anode electrode and immerses an electrolyte. A separator
material suitable for the hybrid supercapacitor described above may
be polyethylene nonwoven fabrics, polypropylene nonwoven fabrics,
polyester nonwoven fabrics, polyacrylonitrile porous separators,
poly(vinylidene fluoride)hexafluoropropane copolymer porous
separators, cellulose porous separators, kraft papers, rayon
fabrics or the like and be any separator which is generally used
for batteries and capacitors.
[0054] Electrolyte
[0055] An electrolyte chargeable to the hybrid supercapacitor
described above may be aqueous electrolytes, non-aqueous
electrolytes, solid electrolytes or the like.
[0056] The aqueous electrolyte may be 5 to 100 wt % of aqueous
sulfuric acid solution, 0.5 to 20 M of aqueous potassium hydroxide
solution, or neutral electrolytes such as aqueous potassium
chloride solution, aqueous sodium chloride solution, aqueous
potassium oxide solution, aqueous potassium sulfate solution and
the like but may not be limited thereto.
[0057] The non-aqueous electrolyte may be an organic electrolyte in
which a salt composed of a cation such as tetraalkylammonium (e.g.,
tetraethylammounium or tetramethylammonium), lithium ion, or
potassium ion, etc. and an anion such as tetrafluoroborate,
perchlorate, hexafluorophosphate, bis(trifluoromethane)
sulfonylimide or trisfluoromethane sulfonylmethide, etc. is
dissolved to be 0.5 to 3 M in a nonprotonic solvent, a solvent
having a high dielectric constant (e.g., propylene carbonate or
ethylene carbonate), or a solvent having a low viscosity (e.g.,
diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate,
dimethyl ether or diethyl ether).
[0058] Further, the electrolyte may be a gel-like polymer
electrolyte, in which a polymer such as polyethylene oxide,
polyacrylonitrile or the like is immersed in an electrolyte, or an
inorganic electrolyte such as LiI, Li.sub.3N or the like.
[0059] FIG. 1 illustrates a schematic view of a hybrid
supercapacitor, including a monolith carbon aerogel cathode, a
monolith transition metal oxide aerogel anode, a separator
separating the cathode and anode, and an electrolyte, according to
an embodiment.
[0060] Hereinafter, although more detailed descriptions will be
given by examples, those are only for explanation and there is no
intention to limit the invention.
EXAMPLE
Preparation of Monolith Carbon Aerogel Cathode
[0061] Resorcinol (R), formaldehyde (F) and sodium carbonate, which
is a basic catalyst, were condensed at an aqueous phase. After the
obtained sol solution was immersed into carbon paper, it was fixed
between glass plates and dried in a closed container to prevent
evaporation of the RF carbon paper and then the remained water was
substituted with acetone to provide a RF aerogel composite immersed
into carbon paper. The RF aerogel composite immersed into carbon
paper was carried for the pyrolysis at a high temperature of
700-1050.degree. C. under N.sub.2 to provide a monolith carbon
aerogel. It was further treated for CO.sub.2 activation in order to
increase effective pores finally to provide a monolith carbon
aerogel having 3-dimensional network structure. As shown in FIGS. 4
and 5, a pore size distribution may be a uniform mesopore size of
20 nm or higher
[0062] The obtained monolith carbon aerogel was cut in an
appropriate size and connected with copper wires to obtain a carbon
aerogel cathode.
Preparation of Monolith Manganese Oxide (MnO.sub.2) Aerogel
Anode
[0063] An aqueous solution of sodium fumarate
(Na.sub.2C.sub.2H.sub.2O.sub.4) was added drop-wise into an aqueous
solution of sodium permanganate (NaMnO.sub.4) while stirring to be
3:1 mole ratio for sodium permanganate:sodium fumarate. After the
reaction solution was stirred for 1 hour, CO.sub.2 was removed by
performing vacuum dressing for 60 minutes. The vacuum dressing
allowed homogenizing of the reaction solution. After the reaction
solution was further stirred for 24 hours, 2.5M H.sub.2SO.sub.4 was
added drop-wise to the reaction solution while stirring. The
reaction solution was stirred for 24 hours and then any soluble
material was removed by washing with water several times. The
solution was filtered and dried to produce manganese oxide aerogel
(Na.sub.xMnO.sub.2+Y.nH.sub.2O).
[0064] The obtained manganese oxide aerogel was cut in an
appropriate size and connected with copper wires to provide a
manganese oxide aerogel anode.
Preparation of Hybrid Supercapacitor
[0065] A hybrid supercapacitor was prepared by employing a working
electrode which used the monolith carbon aerogel electrode as a
cathode and the monolith manganese oxide aerogel electrode as an
anode and copper wires to connect the electrodes without using
binders or current collectors. Aqueous solution of 1M
H.sub.2SO.sub.4 was used as an electrolyte.
Comparison Example
Preparation of Supercapacitor Using Carbon Aerogel Electrode as a
Cathode and an Anode
[0066] Two of monolith carbon aerogel electrodes were prepared by
the same method used to prepare the carbon aerogel in Example and
used as a cathode and an anode to prepare a supercapacitor.
Experimental Example
[0067] The hybrid supercapacitor (carbon aerogel cathode/MnO.sub.2
aerogel anode) prepared in Example and the supercapacitor (carbon
aerogel cathode/carbon aerogel cathode) prepared in Comparison
Example were each determined for electrochemical properties.
[0068] Platinum (Pt) and saturated calomel electrode (SCE) were
used as a counter electrode and a reference electrode, respectively
and an aqueous solution of 1M H.sub.2SO.sub.4 was used as an
electrolyte.
[0069] Cyclic voltammetry was used to determine similar properties
with 2-electrode cells.
[0070] As shown in FIG. 6 (Example) and FIG. 7 (Comparison
Example), both were a little distorted but typical CV shapes of
similar rectangular and mirror image which exhibited fast
reversible charge/discharge process.
[0071] It is noted that the hybrid supercapacitor prepared in
Example (FIG. 6) shows a wider voltage range which provides
improved energy density.
[0072] While it has been described with reference to particular
embodiments, it is to be appreciated that various changes and
modifications may be made by those skilled in the art without
departing from the spirit and scope of the embodiment herein, as
defined by the appended claims and their equivalents.
* * * * *